1. Field of the Invention
This invention relates to the field of power couplers and diplexers. More particularly, the invention relates to a compact waveguide-to-transmission line power coupler and a compact diplexer.
2. Description of the Prior Art
Satellites in earth orbit frequently utilize the same antenna for both transmitting and receiving signals from earth. The frequencies of the transmit signal and the received signal are usually different in such a case to avoid interference between signals. For example, the transmit frequency may be 4 gigahertz, while the signal received by the satellite antenna is 6 gigahertz. Each signal will originate from or be conducted to different equipment within the satellite, so it is necessary to have a three-port component coupling microwave power between the common antenna, and the transmit and receive equipment. This three-port component is usually called a diplexer. It must be capable of efficiently isolating the transmit and receive signals from one another and, for obvious reasons, it should be as light and compact as possible.
Diplexers are generally known and various arrangements have been used aboard satellites in the past. These prior art diplexers have been as short as 6 inches in length and have achieved acceptable isolation between transmit and receive frequencies. For example, one prior art diplexer consists of a first waveguide coupled at one end thereof to a second waveguide, and slot-coupled to a third waveguide through a narrow-wall of the first waveguide. The first waveguide is coupled to the second waveguide through a stepped impedance transformer. This prior art diplexer is relatively large and heavy because of the presence of the stepped impedance transformer. It would be desirable to have a diplexer that is much more compact than prior art devices while providing even better signal isolation.